Method and forming machine for deforming a hollow workpiece

ABSTRACT

The invention relates to a method and a forming apparatus for deforming a hollow workpiece having at least one open end, wherein the workpiece is clamped down in a clamping device, a first forming tool is placed into contact with the outer surface of the workpiece, said workpiece and said tool are rotated about an axis of rotation relative to each other and said workpiece is deformed by means of said first tool. A second forming tool is placed into the cavity defined by the workpiece and into contact with the inner surface of the hollow workpiece, after which the workpiece is deformed by means of said second tool.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a national stage filing and claims priorityof International patent application Serial No. PCT/NL01/00563, filedJul. 20, 2001, and published in English the content of which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The invention relates to a method for deforming a hollow workpiecehaving at least one open end, such as a metal cylinder, for example,wherein the workpiece is clamped down in a clamping device, a firstforming tool is placed into contact with the outer surface of theworkpiece, the workpiece and the tool are rotated about an axis ofrotation relative to each other and the workpiece is deformed by meansof said first tool. A method and forming machine of this kind are knownfor example from European patent application No. EP 0 916 428. Saidpublication discloses a method and a forming machine, comprising aforming head fitted with a number of rollers, by means of which thediameter of one end of a cylindrical metal element is reduced andmoreover bent through an angle.

To this end, the metal cylinder is clamped down and said cylinder andsaid forming head are rotated relative to each other about an axis ofrotation, whereupon said end is deformed by pressing said rollers in aradial direction against the outer surface of said cylinder and movingthem along said outer surface in a number of cycles, whereby the radialdistance between the rollers and the axis of rotation is decreased witheach cycle, as a result of which a reduction of the diameter isobtained. Since the axis of rotation is at an angle with the centralaxis of the metal cylinder, the end of the cylinder is not only reducedas a result of the movement in radial direction of the rollers, but inaddition said end will also be positioned at an angle. Due to the use ofthe aforesaid cycles, the workpiece assumes the shape of the finalproduct step by step.

EP 0 916 426 discloses a comparable method and forming machine, whereinthe axis of rotation is eccentrically offset from the central axis ofthe metal cylinder. Thus a product is obtained wherein the central axisof the deformed portion is likewise offset from the central axis of theundeformed portion of the metal cylinder.

The method and apparatus in hand can be used, for example, in theproduction of the housings of catalytic converters that form part of theexhaust system of vehicles, such as passenger cars. Such catalyticconverters have a diameter which is larger than the diameter of thepipes of the exhaust system of which they form part, and they arepreferably positioned close to the engine block in order to reach theiroperating temperature as quickly as possible after the engine has beenstarted and to maintain that temperature as much as possible. Oneconsequence of this is that, first of all, the diameter of theconnections on either side of the catalytic converter housing must bereduced in order to properly connect to the rest of the exhaust systemand that in addition they often need to have a complicated shape inorder to enable an optimum position with respect to the engine block.

Prior art methods and apparatuses for producing workpieces having atleast one deformed end, such as e.g. the above-described catalyticconverter housings, appear to provide insufficient freedom as regards toshaping. Moreover, it is necessary to use relatively thick-walledworkpieces, since a heavy load is exerted on the material during thedeformation process, which may lead to folds, cracks and/or an irregulardistribution of the wall thickness of the final product. As a result,the obtained products, such as e.g. the aforesaid catalytic converterhousings, are often heavier than is necessary for their properfunctioning in an exhaust system.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate one, some or allof the above drawbacks or at least to alleviate them to a significantextent.

In order to accomplish that objective, the method as referred to in thefirst paragraph includes a second forming tool that is placed into thecavity defined by the workpiece and into contact with the inner surfaceof the hollow workpiece, and the workpiece is deformed by means of saidsecond tool. The forming machine according to another embodiment of thepresent invention includes at least one second forming tool, andpossibly a driver for rotating said second tool, which second tool canbe introduced into the workpiece and placed into contact with the innerwall of the workpiece in such a manner that said wall can be deformed inan outward direction, i.e. in a direction away from the cavity definedby the workpiece.

The use of the second forming tool, such as preferably one or moreforming rollers, provides greater freedom as regards to product designand it makes it possible to deform the workpiece in such a manner thatthe deformed portions extend outside the diameter of the originalworkpiece, which is not possible with the method and apparatus accordingto the above-described prior art. If the workpiece is a metal cylinder,this means that after deformation, the deformed end(s) will liepartially or entirely outside the circumference of the undeformed partof the metal cylinder.

Moreover, the load that is exerted on the workpiece during thedeformation process can be considerably reduced, so that it will bepossible to form workpieces having a relatively small wall thickness aswell. A minimum wall thickness of the cylindrical starting material of1.5 mm is frequently used for the aforesaid housings for catalyticconverters, while the invention makes it possible to deform materialshaving a smaller wall thickness of, for example, 1.2 mm or less.

Complex shapes can be obtained by pivoting the clamping device on theone hand and the tools on the other hand relative to each other about atleast one axis during said deformation and/or between deforming steps(on the same workpiece). Pivoting about two or more axes, wherein atleast two of said axes, or the projections of each of said axes on acommon plane, are at an angle (for example of 90°) with respect to eachother, makes it possible to produce complex shapes in variousdirections.

The invention furthermore relates to a hollow workpiece having acontinuous wall and at least one open end, which has been deformed,preferably by means of the above-described method, wherein at least partof the edge of said end lies outside the circumference of the workpieceafter deformation. Such a workpiece preferably comprises a substantiallycylindrical or oval metal body or at any rate a body which can bedeformed by means of the present method, having two open ends which havebeen deformed in such a manner that at least part of the edge of atleast one of the two ends lies outside the circumference of anundeformed portion of the workpiece, wherein the projections of thecentral axes of said ends on a plane straight through an undeformed partof the metal body are at an angle of less than 180° with respect to eachother.

In addition to this, the invention relates to a catalytic converter fora vehicle, such as e.g. a car, comprising such a workpiece.

For the sake of completeness, it is noted that Japanese patentapplication no. 08-224625 describes the manner in which the diameter ofthe neck of a can is reduced by means of forming rollers while adetainer is present in the can. Said detainer only functions to supportthe inner surface of the neck of the can, it is not used for deformingsaid neck.

The invention will now be explained in more detail with reference to theappended figures, which show a number of embodiments of the method andthe apparatus according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top plan view, partially in section, of a formingmachine according to the present invention, comprising two forming headsand a stationary workpiece.

FIG. 2 is a side elevation of the forming machine of FIG. 1.

FIG. 3 is a side elevation of the forming machine of FIG. 1, wherein apart of the forming machine is turned through an angle of 90°.

FIGS. 4 and 5 schematically show a number of stages of a methodaccording to the present invention, carried out on the forming machineof FIG. 1.

FIGS. 6 and 7 are schematic top plan views, partially in section, of asecond embodiment of the forming machine according to the presentinvention comprising a single forming head and a rotatable workpiece.

FIG. 8 is a schematic top plan view, partially in section, of a variantof the forming machine according to FIGS. 6 and 7.

FIG. 9 shows a number of stages of a second method according to thepresent invention, carried out on the forming machine of FIGS. 6 and 7.

FIGS. 10, 11 and 12 are schematic top plan views, partially in section,of a fourth embodiment of the forming machine according to the presentinvention, by means of which the workpiece can be rotated.

FIGS. 13 and 14 schematically show a number of stages of a second methodaccording to the present invention, carried out on the forming machineof FIGS. 10-12.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Parts corresponding to each other or having substantially the samefunction in the various embodiments will be indicated by the samenumerals.

FIG. 1 shows a forming machine 1, comprising a first forming head 2, asecond forming head 3 and a chuck 4 for clamping down the workpiece, forexample the illustrated, already deformed, metal cylinder 5. The twoforming heads 2, 3 comprise a baseplate 6 on which two guide rails 7 aremounted. Guides 8 extend over said rails 7 on which guides a second setof guide rails 9 is mounted, which guide rails extend at right angles tosaid first rails 7. Present on said second set of rails are guides 10,which support a housing 11, in which an assembly 12, comprising formingrollers 13 and means for moving said forming rollers 13, is mounted inbearings 14.

Each of the forming rollers 13 is rotatably mounted on one end of a rod15, which is in turn mounted on or forms part of a wedge-shaped element16, which widens in the direction of forming rollers 13. Forming rollers13 and their respective rods 15 and wedge-shaped elements 16 can each bemoved radially inwards and outwards relative to the axis of rotation 17of assembly 12. To this end, each of the wedge-shaped elements 16 ismounted on a wedge-shaped guiding mandrel 18, whose thickness decreaseslinearly in the direction of forming rollers 13, in such a manner thatwedge-shaped elements 16, and thus rods 15 and rollers 13, are forcedradially towards axis of rotation 17 upon outward movement (to the rightin the drawing) of mandrels 18, and radially away from axis of rotation17 upon inward movement (to the left in the drawing) thereof.

In accordance with the invention, assembly 12 furthermore comprises aforming roller 19 (hereinafter called inside roller 19), which ismounted in assembly 13 in substantially the same manner as formingrollers 13, i.e. rotatably mounted on one end of a rod 20, which is inturn mounted on or forms part of a wedge-shaped element 21, which widensin the direction of forming inside roller 19. The element 21 is mountedon a wedge-shaped mandrel 22, in such a manner that the element 21, andthus rod 20 and roller 19 are forced radially towards the axis ofrotation 17 upon outward movement of mandrel 22 and radially away fromaxis of rotation 17 upon inward movement thereof.

In FIG. 1, inside roller 19 has been moved into workpiece 5 and has beenplaced into contact with the inner wall of workpiece 5. The wall ofworkpiece 5 can be deformed in outward direction, that is, in radialdirection away from the cavity 5 defined by workpiece 5, by means ofsaid inside roller 19. Forming rollers 13 and inside roller 19 often liein the same plane, which plane extends perpendicularly to axis ofrotation 17 in this embodiment, so that the wall is confined betweensaid rollers 13, 19 at the location of the deformation.

Assembly 12 comprises an external gear 25 on a side remote from rollers13, 19, which gear mates with a pinion 26 mounted on the end of a driveshaft 27 of an electric motor 28. Thus, the assembly 12 can be rotatedby means of a driver, herein an electric motor 28, gear 25 and pinion26.

Assembly 12 furthermore comprises an actuator herein a hydrauliccylinder 29, which is capable of moving ring 18, and thus formingrollers 13, in radial direction by means of a piston 30, a piston rod 31and a pressure plate 32. Within the framework of the presentdescription, the radial movement of the forming rollers 13 will beindicated as the Z-direction.

Ring 22, and thus inside roller 19, can be moved in radial direction bymeans of an actuator, herein a hydraulic cylinder 33 and a hollow pistonrod 34, while housing 11 can be moved along said guide rails 7 and 9 inits entirety by means of actuators, herein hydraulic cylinders 35 and36. Within the framework of the present description, the radial movementof inside roller 19 will be indicated as the W-direction. Movements ofhousing 11 parallel to axis of rotation 17 and perpendicularly to saidaxis 17 will be indicated as the X-direction and the Y-direction,respectively.

Second forming head 3 is practically identical to forming head 2, but itis furthermore capable of pivoting movement about a pivot point 37, sothat the end of workpiece 5 that is being worked by said forming head 3can be deformed through an angle of 90°, for example. In addition, anassembly 38 is provided, by means of which axis 37 can be moved, as willbe explained in more detail hereafter.

FIGS. 4 and 5 schematically show in 25 steps the manner in which an openend of a metal cylinder 5 can be deformed by means of forming head 3 offorming machine 1 according to FIG. 1. At the same time, the other endof cylinder 5 can be worked by means of forming head 2. Step 1 shows thestarting position, wherein workpiece 5 is clamped down in a chuck 4.Said end, which has already undergone a machining step and which has asmaller diameter than the other part of cylinder 5, is then (step 2)deformed by rotating assembly 12 and placing the forming rollers 13, 19into contact with, respectively, the outer surface and the inner surfaceof cylinder 5 and moving said rollers radially towards axis of rotation17 and away from axis of rotation 17, respectively, and simultaneouslypivoting the forming head through an angle β about pivot point 37. Thevarious driving means are thereby controlled in such a manner that acomposite, flowing movement of the forming rollers 13, 19 (inZ-direction and W-direction), assembly 13 (in X-direction andY-direction) and the forming head (through an angle β) is obtained, as aresult of which a bent portion 40 is formed.

After forming head 3 has been pivoted through an angle β, the movementof the assembly 12 in the X-direction is continued (step 3), so that acylindrical portion 41 remains, which portion has a smaller diameterthan the original open end of cylinder 5 and which extends at an angle βrelative to the other part of cylinder 5.

Then (step 4) the forming rollers 13, 19 are moved radially outwards andradially inwards, respectively, so that the contact between said rollers13, 19 and, respectively, the outer surface and the inner surface of thewall of cylinder 5 is broken. Assembly 12 is moved back alongcylindrical portion 41 in the X-direction and the Y-direction until thetransition between the bent portion 40 and said cylindrical portion 41.

The above cycle is repeated by pivoting forming head 3 through an angleβ and translating and adjusting assembly 12 (step 5, which issubstantially identical to step 2) and translating assembly 12 in theX-direction and the Y-direction (step 6, which is substantiallyidentical to step 3), wherein the diameter of the cylindrical portion 41is further reduced. Then the contact between said rollers and saidcylindrical portion 41 is broken, and the assembly is returned to thetransition area between bent portion 40 and cylindrical portion 41 (step7, which is substantially identical to step 4).

Depending on the characteristics of the workpiece, such as the wallthickness, the mechanical strength and stiffness and the elasticelongation, steps 2-4 are repeated until the desired reduction of thediameter and the desired angle, for example of 90°, have been obtained.If the nature of the workpiece involves that the angle β must not belarger than, for example, 15 or 8 per cycle, a total number of,respectively, 6 and 12 cycles will be required for the said deformation.

After the operations that are shown in FIG. 4 have been carried out,pivot point 37 is moved by means of assembly 38 to the starting positionas shown in FIG. 5 (step 13). The operation of FIG. 4 (steps 2-12) arerepeated (steps 14-25), wherein the angle β is of opposite sense,however, so that an S-bend is obtained in the end of cylinder 5.

As is shown in FIG. 3, the forming head 3 of forming machine 1 isfurthermore capable of pivoting movement about axis of rotation 17 offorming head 2, so that the bending of workpiece 5 is not limited tobending in one and the same imaginary plane. Pivoting of forming head 3about axis of rotation 17 between or during operations enables thecentral axis of the deformed portion of workpiece 5 to assume athree-dimensional shape.

FIGS. 6 and 7 show a second and relatively simple embodiment of theforming machine 1 according to the present invention, wherein workpiece5 is clamped down, in a manner which is known per se, in a rotatablechuck 60 which is mounted in a spindle casing 61 and which can berotated about an axis 17 by means of a drive such as an electric motor(not shown). A forming head 62 comprises an assembly 12, which isstationary and which need not be rotated, although driving means may beprovided, of course, if an exceptionally high rotational speed of theassembly 12 relative to the workpiece 5 is desired. FIG. 8 shows avariant of the forming machine 1 according to FIGS. 6 and 7, whereinforming rollers 13 and inside roller 19 each form part of their ownassembly 12, 12′. This makes it possible to control inside roller 19fully independently of forming roller 13, which may be desirable forspecific products.

FIG. 9 schematically shows in 12 steps the manner in which an open endof a metal cylinder 5 can be deformed by means of forming head 62 offorming machine 1 according to FIGS. 6 and 7. Step 1 shows the startingposition, wherein workpiece 5 is clamped down in a chuck 60. Said end,which has already undergone an operation and which has a smallerdiameter than the other part of cylinder 5, is then (step 2) deformed byrotating chuck 60 and placing the forming rollers 13, 19 into contactwith, respectively, the outer surface and the inner surface of cylinder5 and moving said rollers radially towards axis of rotation 61 and awayfrom axis of rotation 61, respectively (step 2), and subsequentlyadjusting assembly 12 a distance y in the Y-direction. Then the assembly12 is translated in the X-direction is continued (step 3), so that aneccentric, cylindrical portion 41 remains, which portion has a smallerdiameter than the original open end of cylinder 5 over a distance y.Then (step 4) the forming rollers 13, 19 are moved radially outwards andradially inwards, respectively, so that the contact between said rollers13, 19 and, respectively, the outer surface and the inner surface of thewall of cylinder 5 is broken. Assembly 12 is moved back into cylindricalportion 41 in the X-direction, to the X-position in the startingposition.

The above cycle is repeated by adjusting assembly 12 over a distance y(step 5, which is substantially identical to step 2) and translatingassembly 12 in the X-direction (step 6, which is substantially identicalto step 3), wherein the diameter of the cylindrical portion 41 isfurther reduced.

Depending on the characteristics of the workpiece, steps 2-4 arerepeated until the desired reduction of the diameter and theeccentricity have been obtained, wherein the wall of the deformedportion may lie outside the circumference of the other part of thecylinder.

FIGS. 10-12 show a fourth embodiment of the forming machine 1 accordingto the present invention, wherein workpiece 5 is not only capable ofbeing rotated, but also of being pivoted about a pivot point 65. To thisend a chuck 66 is mounted in a slot 67 in a housing 68. Said housing 68is rotatably mounted in a frame (not shown) and furthermore compriseshydraulic cylinders 69, 70 for radial adjustment of chuck 66, a gauge(not shown) for measuring the radial movement of chuck 66, acounterweight 72 for balancing the whole and a gauge (not shown) formeasuring the pivoting of workpiece 5.

FIGS. 13 and 14 schematically show in 25 steps the manner in which anopen end of a metal cylinder 5 can be deformed by means of forming head3 of forming machine 1 according to FIG. 1. Step 1 shows the startingposition, wherein workpiece 5 is clamped down in a chuck 4. Said stepsare similar to the steps of FIGS. 4 and 5, wherein the movement of pivotpoint 37 is effected by moving assembly 12 in the X-direction and theY-direction.

As a matter of course the forming machines according to the presentinvention can be operated by a person as well as by a control unit. Sucha control unit is for example arranged for controlling the means formoving the rollers in X-direction, Y-direction and radial direction inaccordance with a control program that is stored in a memory, in such amanner that the forming rollers follow one or more desired paths fordeforming the workpiece into the desired product or intermediateproduct.

Although the invention has been explained on the basis of a cylindricalmetal workpiece in the foregoing, it is also possible to implement theinvention on workpieces of unround section, such as e.g. an oval, asubstantially triangular or a multilobal section.

Consequently, the invention is not restricted to the above-describedembodiments, which can be varied in several ways without departing fromthe scope of the invention as defined in the claims.

1. A method for deforming a hollow workpiece having at least one open end, wherein the workpiece is clamped down in a clamping device, a first forming tool is placed into contact with the outer surface of the workpiece, at least one of said workpiece and said first forming tool are rotated about an axis of rotation relative to each other and said first forming tool follows one or more desired paths with respect to the workpiece with a component parallel to the axis of rotation so as to work said workpiece; and wherein a second forming tool is placed into the cavity defined by the workpiece, and into contact with the inner surface of the hollow workpiece, and the workpiece is deformed beyond the end of the workpiece by means of said second forming tool.
 2. The method according to claim 1, wherein said workpiece and said first and said second forming tools are rotated relative to each other about the axis of rotation which extends at least one of eccentrically and at an angle with a central axis of the clamped-down workpiece.
 3. The method according to claim 1, wherein said first and second forming tools rotate in at least substantially the same plane during at least part of the operation.
 4. The method according to claim 1, wherein the clamping device and said first and second forming tools are pivoted about at least one axis relative to each other during said deformation and/or between deforming steps on the same workpiece.
 5. The method according to claim 4, wherein said clamping device and said first and second forming tools are pivoted about at least two axes relative to each other during said deformation and/or between deforming steps wherein at least two of said axes, or the projections of each of said axes on a common plane, are at an angle with respect to each other.
 6. The method according to claim 5, wherein at least one of said axes is moved during said deformation and/or between deforming steps.
 7. The method according to claim 1, wherein a larger part of the deforming is carried out in one flowing movement.
 8. A forming machine comprising: a clamping device for clamping down a hollow workpiece to be deformed, which has at least one open end; a first forming tool being placeable into contact with the outer surface of the workpiece while the workpiece is being worked to cause deformation in an inward direction; a driver configured to rotate at least one of said workpiece and said first forming tool relative to each other about an axis of rotation, such that said first forming tool is able to follow one or more desired paths with respect along the workpiece with a component parallel to the axis of rotation so as to work said workpiece; and at least one second forming tool, being insertable into the workpiece and placed into contact with an inner wall of the workpiece, such that said wall is deformed outwards.
 9. The forming machine according to claim 8, wherein said driver is adapted to rotate said workpiece and said first and said second forming tools relative to each other, about an axis of rotation which extends at least one of eccentrically and at an angle with a central axis of the workpiece.
 10. The forming machine according to claim 8, wherein said clamping device and said first and second forming tools are pivotable relative to each other about at least one axis.
 11. The forming machine according to claim 10, wherein the clamping device and the first and second forming tools are pivotable about at least two axes, wherein at least two of said axes, or a projection of said axes on a common plane, are at an angle with respect to each other.
 12. The forming machine according to claim 11, wherein at least one of said axes is movable.
 13. The forming machine according to claim 8, wherein the clamping device for the workpiece is rotatable.
 14. The forming machine according to claim 13, wherein a chuck for clamping down the workpiece is pivotally and translatably mounted in said clamping device.
 15. The forming machine of claim 8 wherein the second forming tool is configured to deform the workpiece beyond the end of the workpiece.
 16. A method for deforming a hollow workpiece having at least one open end, the method comprising: clamping the workpiece in a clamping device; engaging an outer surface of the workpiece with a first forming tool and working the workpiece, wherein said first forming tool follows one or more desired paths with respect to the workpiece with a component parallel to the axis of rotation so as to work said workpiece; rotating at least one of said workpiece and said first forming tool about an axis of rotation relative to each other and; and engaging an inner surface of the workpiece with a second forming tool through the open end into a cavity of the workpiece and applying force with the second forming tool so as to deform the wall between the inner surface and the outer surface outwardly.
 17. The method of claim 16 engaging the inner surface of the workpiece and applying force includes deform the workpiece beyond the open end of the workpiece.
 18. The method according to claim 17 and further comprising rotating said first and said second forming tools relative to each other about the axis of rotation which extends at least one of eccentrically and at an angle with a central axis of the clamped-down workpiece.
 19. The method according to claim 18, wherein said first and second forming tools rotate in at least substantially the same plane during at least part of the operation.
 20. The method according to claim 18 and further comprising pivoting the clamping device and said first and second forming tools about at least one axis relative to each other during deformation of the workpiece and/or between deforming steps on the same workpiece. 